43 lines
1.4 KiB
Java
43 lines
1.4 KiB
Java
import java.awt.Point;
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import java.util.ArrayDeque;
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import java.util.List;
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import java.util.Queue;
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public final class TopicVariable {
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public static void main(String[] args) {
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List<Integer> numbers = List.of( 1, 2, 3, 4, 5, 6, 7, 8, 9 );
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// Example 1:
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// We only want to count the number of elements in a list,
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// so a topic variable can be used for the identify of each element of the list.
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// An artificial example since we could just use 'total = numbers.size()'.
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int total = 0;
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for ( Integer _ : numbers ) { // Topic variable
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total += 1;
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}
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System.out.println("The list contains " + total + " numbers");
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// Example 2:
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// A topic variable is suitable for the unused identifier of the NumberFormatException.
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String text = "123456:@~";
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int i = 0;
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try {
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i = Integer.parseInt(text);
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} catch(NumberFormatException _) { // Topic variable
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System.out.println("Variable i is incorrectly defined with value: " + i);
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}
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// Example 3:
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// We only require the first two out of every three items in a queue.
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// A topic variable can be used for the third unused item.
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Queue<Integer> queue = new ArrayDeque<Integer>(numbers);
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while ( queue.size() >= 3 ) {
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int x = queue.poll();
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int y = queue.poll();
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int _ = queue.poll(); // Topic variable
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System.out.println( new Point(x, y) );
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}
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}
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}
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